1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, printer or facsimile machine, an image erasing apparatus for erasing images formed by the image forming apparatus, and an image forming-erasing system including an image forming apparatus and an image erasing apparatus.
Specifically, it relates to, as the image forming apparatus, an electrophotographic image forming apparatus, in which an image is formed using a powdery thermoplastic image-forming material and to, as the image erasing apparatus, an image erasing apparatus, in which an image on a recording medium is erased by heating the image-forming material on the recording medium, overlaying the heated image-forming material on the recording medium with a stripping member, and separating the stripping member from the recording medium to thereby transfer the image-forming material from the recoding medium to the stripping member.
It also relates to a digital image forming apparatus such as a digital copying machine, a digital printer or a digital facsimile machine, in which an image is formed according to digital signal processing.
The present invention can be advantageously applied to an image forming process using a powdery thermoplastic image-forming material to form an image, as well as to the case where an image can be erased only according to a specific image forming process using a recording medium having specific properties. In the latter case, the present invention can serve to avoid troubles occurred when an inerasable image is formed or when an image-inerasable recording medium bearing an image is conveyed to image erasing unit.
2. Description of the Related Art
Printers, copying machines and printing machines of electrophotographic system have become wide spread and paper as a recording medium has been consumed in a large quantity. Such paper generally used as the recording medium is made from pulp derived from wood. Volume consumption of paper leads to deforestation and deteriorates the terrestrial environment. Reducing the consumption of paper has become a challenge of the society. In addition, waste disposal has limitations in its space and cost, and reducing the waste also has become a challenge for the society.
To solve these problems, information recording paper which becomes unnecessary (waste paper) is recovered, disintegrated to pulp and reused according to a conventional technique. This technique, however, consumes a large quantity of energy for transporting the waste paper and for regenerating the pulp, and the resulting recycled paper has decreased rigidity and whiteness and invites image bleed when an image is printed thereon. In addition, recording media bearing recorded information are distributed out of companies and home, inviting problems in protection of security and personal privacy.
Techniques for recording, processing, transmitting and storing images as electronic information have been developed, and images are recorded and stored on paper and transmitted in markedly reduced occasions. However, when one peruses the contents of WebPages or information stored in database on a display, the efficiency of perusal may be low or the eyes may fatigue. In such cases, an increasing demand has been made to record an image to a recording medium temporarily for perusing, where the storage of the image is not required. However, no effective system has been developed for forming an image and erasing the image to thereby regenerate and reuse recording media even in the case the image is required temporarily. In particular, a strong demand has been made to provide a system that can completely erase a formed image for protection of security and personal privacy.
Japanese Patent Application Laid-Open (JP-A) No. 01-297294 discloses a method for erasing or eliminating an image on a recording medium. This method uses an image bearing member such as a plastic, a metal, a liquid-impermeable paper or ceramic and comprises the step of heating a hot melt image on the image bearing member (recording medium) with the interposition of a hot melt stripping member to thereby transfer the image to the stripping member (ink stripping member).
JP-A No. 02-55195 discloses use of a recording medium comprising a substrate such as a polyethylene terephthalate (PET) film and a releasing material such as a silicone sealant arranged on the substrate as an erasable recording medium.
JP-A No. 04-67043 discloses an erasable paper comprising a coated paper and a film of a silicone sealant arranged on the coated paper and having a mark formed with a writing instrument or a hole for distinguishing the erasable paper from regular paper.
JP-A No. 04-64472 discloses an image erasing apparatus. This apparatus uses an erasable paper comprising paper and a film of a silicone sealant formed on the paper or comprising paper and a plastic film applied onto the paper. The apparatus is so configured as to heat an image formed on the erasable paper, and an endless belt having a hot-melt resin on its surface, to bring the image and the endless belt into contact with each other, to cool the contacted image and the endless belt, to separate the erasable paper from the endless belt to thereby transfer and peel off the image from the erasable paper to the endless belt. The publication also discloses a technique, in which a mark is imparted to the erasable paper, the erasable paper is distinguished from a regular paper by detecting the mark, and the regular paper, if used, is by-passed so as not come in contact with the endless belt having the hot-melt resin on its surface to avoid paper attachment onto the endless belt. Thus, the endless belt is prevented from losing its function as a cleaning sheet.
JP-A No. 09-179452 and No. 09-179453 disclose image forming apparatuses. The disclosed image forming apparatuses are so configured as to form an image according to a first image-forming mode and a second image-forming mode. The apparatuses forms an image using a synthetic paper which does not absorb a toner, and an alcohol-soluble image-forming material according to the first image-forming mode and forms an image using a regular paper and a regular plastic toner according to the second image-forming mode. An image formed by the image forming apparatuses is removed from a recording medium with the use of an alcohol.
JP-A No. 07-239635 discloses an image forming apparatus which is so configured as to be able to select a first image-forming mode and a second image-forming mode. According to the first image-forming mode, an image is formed under regular conditions for image formation. According to the second image-forming mode, an image is formed under such conditions that ease the formed image to be erased. In the second image-forming mode, the amount of a toner applied to a recording medium is reduced by changing, for example, the exposure or development bias voltage from the first image-forming mode. The publication also discloses that a mark is imparted to entire or part of the recording paper so as to enable a user to recognize the image printed according to the second image-forming mode when the image is formed according to the second image-forming mode.
JP-A No. 07-239632 discloses an image forming apparatus, in which a mark indicating whether or not an image-erasing operation can be carried out is imparted to part of a recording medium by an image erasing apparatus. It also discloses an image forming apparatus in which a mark for prohibiting an image-erasing operation is imparted to a recording medium so as to protect a document which should not be erased from erasing by mistake, and discloses impartment of a mark for allowing an image-erasing operation.
JP-A No. 2001-209274 discloses an image forming apparatus that can use a reusable paper. In this apparatus, a reusable paper is automatically selected typically in a test printing mode, and a regular paper other then the reusable paper is automatically selected typically in a finishing mode. In the finishing mode, the printed paper is subjected to a processing such as punching. According to this technique, there is no necessity for a user to determine whether or not a reusable paper should be used.
JP-A No. 2001-209284 discloses an image forming apparatus, in which an image is formed on a reusable paper in an area where an image is erasable, and information indicating whether or not the image is erasable is recorded thereon. The information herein includes, for example, the number of usable times of the recording medium, image occupancy and type of the toner.
JP-A No. 2001-334649 discloses an image forming apparatus which works in a first image-forming mode for forming an image on a regular recording medium and a second image-forming mode for forming an image on a reusable recording medium. In the apparatus, image formation is automatically carried out based on specific information typically on whether or not a reusable recording medium is housed in a paper feed cassette or on the type of an application to which the selection of the mode is outputted.
These conventional techniques separately and respectively disclose a technique comprising use of a reusable recording medium from which an image is easily erased and formation of an identification means on the reusable recording medium; a technique in which a mark for prohibiting or permitting image erasing is imparted to a recording medium upon image formation based on whether or not a target document should be protected from erasing; and a technique of detecting whether or not a reusable recording medium is housed in a paper feed cassette.
The systems disclosed in these conventional techniques may invite some troubles as shown below. For example, if an image is printed on a reusable paper by a printer of a system according to which the resulting image is inerasable and the resulting reusable paper carrying an inerasable image may be fed to an image erasing apparatus, thus inviting troubles. If reusable recording media are mixed with regular recording media and fed to an image erasing apparatus, they may also invite some troubles in the apparatus. These problems are typical in a specific type of image erasing apparatuses. In these image erasing apparatuses, an image-forming material is eliminated from a recoding medium to regenerate the recording medium by heating and pressurizing the recording medium and a stripping member to intimate contact, then separating the stripping member from the recording medium to thereby transfer the image-forming material from the recording medium to the stripping member. According to this system, the stripping member cannot be significantly separated from the recording medium if the recording medium is an image-inerasable recording medium or a reusable recording medium bearing an image formed from an inerasable image-forming material. This invites jamming of the recording medium in the image erasing apparatus. In addition, such conventional image forming-erasing systems are not configured integrally. More specifically, the components of the systems, such as an image forming process for easier erasing of the resulting image, a reusable recording medium and an apparatus for forming a reusable image, are not well organized. Thus, an image is not completely removed or eliminated by image erasing operation, or a recording medium after an image-erasing operation has some deteriorated properties. In other words, there is no effective system for fully erasing an image and avoiding troubles in an image erasing apparatus even in the case where there is no necessity for the image to be printed permanently. Taking transactions for meeting as an example, it is effective to print out information on paper and peruse the printed matter during meeting, but it is not preferred for attendees to store the printed matter as a paper document after the meeting, since such stored paper documents are difficult to be surveyed and occupy a large space. The information is thus preferably stored and distributed as electronic information before or after the meeting or stored as common database on the electronic information for the attendees. On perusing stored electronic information, however, it is efficient to print out the information as an image on a sheet recording medium. Such stored electronic information can be perused on a display, but perusing the information on the display is not efficient, since a plurality of pages cannot be viewed at glance, it takes a long time to reach a target page, and the entire document cannot be significantly overviewed. The information is often confidential. Thus, when an image formed on a recording medium is perused temporarily and is then erased, the image must be fully erased to avoid a residual image even if it is a thin image. Conventional image erasing apparatuses cannot fully erase an image to such a degree that the resulting image cannot be recognized at all.
Objects and Advantages
Accordingly, an object of the present invention is to solve the problems in conventional techniques. More specifically, an object of the present invention is to provide a method or device for forming an image on a recording medium in the case where a user wants to reuse the recording medium. Another object of the present invention is to provide a technique for fully erasing an image on a recording medium, which image is formed provided that the recording medium is reused, by an image-erasing device to such a degree that a residual image, if any, after image erasing cannot be recognized at all, as in the use of a shredder. Yet another object of the present invention is to avoid troubles occurred in an image erasing apparatus due to imperfect erasing (removal) of an image and is particularly to avoid troubles such as jamming of recording media in a specific type of image erasing apparatuses. In this type of image erasing apparatuses, an image-forming material is eliminated from a recoding medium to regenerate the recording medium by heating and pressurizing the recording medium and a stripping member to intimate contact, then separating the stripping member from the recording medium to thereby transfer the image-forming material from the recording medium to the stripping member. A further object of the present invention is to provide an image forming apparatus, an image erasing apparatus and an image forming-erasing system, in which an image temporarily formed on a recording medium by the image forming apparatus is fully or completely erased or eliminated to such a degree that a remained image, if any, cannot be recognized by any way such as visual observation.